My many hats February 9, 2012
Posted by mareserinitatis in computers, engineering, gifted, homeschooling, math, teaching, work, younger son.Tags: division, minion, software, work, younger son
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A couple weeks ago, my blog was promoted by a couple of sites and the hits started flowing in. I commented to someone (most likely Gears) how it’s nice to be recognized for my blogging about engineering but frustrating for the lack of recognition for my actual engineering work. Guess I should’ve waited a couple weeks.
Normal work has also been crazy. I’ve been given full control of the Minion and have thrown him in on a new project where he’s learning everything from scratch. It’s similar to projects that I’ve done, but even more complicated and using a different program. So our next couple weeks are going to be real fun as we’re going to be trying to make our way through using this new program and occasionally resorting to the old program for reality checks.
The other serious challenge I’ve been dealing with this week is long division. It’s pretty scary stuff, especially when you have a seven-year-old who is fighting some rather strong perfectionistic tendencies. He’s been getting to the long division portions in his computer math, and he starts to shut down. I’ve been getting more and more frustrated with it, so I decided to put an end to it tonight. I went back and printed out some of the older homeworks so that we could take a couple steps back. I think the problem is that he really thinks he can do everything in his head. I have to admit that his ability to do mental math far outweighs mine: I simply have to write everything down. However, he’s starting to hit the limit of this particular ability, and so he freaks out whenever he has to do a problem where he can’t do it all in his head.
I told him that tonight’s homework was going to be doing some work sheets. With the problems written out on paper, he didn’t seem to have this idea that he had to do everything in his head. The first couple were challenges, but then he started getting the hang of things and was able to execute the last few problems very quickly. By the time we had finished, he was doing 3-digit numbers divided by 2-digit numbers with no problem. We’re going to do some more difficult problems tomorrow and then try heading back to the computer.
We tried a similar approach when he started to get stuck on multiplication a couple months ago. I guess there are some things that really have to be written out to be understood. I just hope he starts to make regular use of his notebook from here on out.
Wordless Wednesday: Hoarfrost makes North Dakota winters beautiful February 8, 2012
Posted by mareserinitatis in Fargo, photography, younger son.Tags: fargo, hoarfrost, winter, younger son
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How I can tell the younger son is my child… January 28, 2012
Posted by mareserinitatis in math, younger son.Tags: math, minus, negative numbers, younger son
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The younger son is learning how to manipulate negative numbers in math. However, he was getting very irritated when listening to the ‘lectures’ yesterday. The lecture would use the term ‘minus’, as in -6 is pronounced ‘minus six’. Every time it did that, the younger boy would make some exasperated grunt and say, loudly, “Negative!”
I can only think this may be because I always call them ‘negative’. The term minus, to me, implies an operation. If so, he obviously picks up on subtleties a lot better than I thought.
When you think of a scientist… January 26, 2012
Posted by mareserinitatis in science, societal commentary, younger son.Tags: science, women in science, younger son
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On the way to school yesterday, the younger boy started telling me that Dr. Frankenstein wasn’t a real scientist. I asked him what he thought of when he heard the word scientist. He was very quiet, and I started feeling anxious that this was going to end up in a “dude in a lab coat with beaker”.
I interjected, “You think of your mom, right?”
“No,” he paused for a few moments more. ”I think of someone who is already dead.”
Oh great. So to be a scientist, you can only be recognized post-mortem, right? I wondered if it was someone crazy like Tesla.
“Already dead?”
“Yeah, she discovered radium, I think.”
I was kind of stunned. He wasn’t thinking of guys in lab coats – he was thinking of Marie Curie. Upon conversing further, it turned out that he knew quite a bit about her. There was a Magic School Bus book on science fairs at his classroom, and he had read about her in there.
I had to admit that I was hugely relieved that not only did he suffer from a common misconception about what a scientist is but that his first thought of a scientist was actually a very accomplished female scientist.
Although I’m still a tiny bit sad he didn’t think of me.
Pinewood derby: What a drag! January 16, 2012
Posted by mareserinitatis in engineering, physics, science, younger son.Tags: air resistance, cub scouts, drag, energy, energy conversion, friction, gravitational energy, physics, pinewood derby
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My husband son competed yesterday in my son’s his scouting group’s pinewood derby race. For those of you who have never had a kid in cub/boy scouts, they hand out these blocks of wood that you get to make into a car. The idea isn’t to win the race: it’s supposed to be that dads and their boys spend some time bonding over manly things like woodworking.
(One year, Mike was out of town during this whole thing, so I got to be manly and help the older boy build his car. All I can say is that Dremel tools are awesome.)
If you look on the web, you’ll find a lot of advice on how to prep pinewood derby cars and make them faster. One thing that consistently bugs me is that one should pay attention to aerodynamics of the car and give it a low profile.
This makes me nuts.
To understand the following, you might want to know what a track looks like. So here you go:
Let’s start out with the specifications. Most pinewood derby tracks have a height of about 4 feet and a length of 32 feet. I also will note that the ones we’ve raced on were wood, not aluminum.
Most of the pinewood derby cars I watched made it the whole 32 feet, though not all did. So let’s say that, on average, they travel 32 feet. The *fastest* ones traveled at an average speed of 10 ft/s (or 3 m/s). The maximum they can weight 5 oz. or 140 g.
What we’re going to do here is look at how much energy the system puts into overcoming air resistance versus friction. It’s very hard to figure out exactly how much goes into friction simply using equations, so we’re going to figure out the total energy and the energy lost to drag forces. Once we have those two quantities, we can subtract the drag forces from the total energy and assume that the difference is equal to the frictional losses. Finally, we can compare the drag and frictional losses.
First things first: what is our total energy? It starts out entirely as potential energy as the cars are placed at rest on the top of the ramp. Potential energy is, fortunately, very easy to calculate. It is simply the product of the height of the object, its mass, and the gravitational acceleration. In other words,
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We know the mass of the car (0.14 kg), the height is approximately 1.22 m, and the graviational acceleration is 9.8 m/s2. This results in a total potential energy of approximately 1.67 J.
The potential energy is equal to the total energy in the system since the cars start with no other kind of energy. In a frictionless and drag-free system, all of this energy would be converted to kinetic energy and the cars would drive forever at the same speed once they reached the bottom of the ramp. Obviously, however, that’s not what happens. Eventually, all of the energy is converted to friction and drag, and the cars stop.
Now we need to determine the drag on the cars. The drag equation is:
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The drag force is proportional, therefore, to the density of the fluid (ρ), velocity (v), drag coefficient (CD), and cross-sectional area (A).
The density of the fluid (air) is approximately 1.2754 kg/m3, and the velocity is 3 m/s. The cross-sectional area of the car, at maximum, is 2.75 x 3 in. In real *ahem* units, this is 0.00532257 m2.
The drag coefficient for a long cylinder, according to Wikipedia, is 0.82. Given the cars are all sorts of different shapes, I think this would probably be the closest approximation, although for some cars, this will be high.
All of this put together gives us a force of 0.025 N. Over a distance of 32 feet (or 9.75 m), this gives an energy of 0.24 J.
If we assume that all of the potential energy is converted to either drag or friction, that means 0.24 J is converted to drag while 1.43 J goes into friction. This means that roughly 14% of your energy losses are due to drag while the other 86% are due to friction.
My advice, therefore, is to not worry so much about drag and the aerodynamics of the car and to worry far more about the ways to reduce friction.
What should you do to help your pinewood derby car to be fast? There are three things:
1) You want to maximize your potential energy, so being as close to the 140 gram maximum weight is good. You can get all sorts of weights commercially to assist with this. Some people have argued that putting the weights near the back of the vehicle helps even more. I wouldn’t doubt this as you’re putting the weight at greater height, giving the car more initial energy to start with.
2) The biggest issue is reducing the friction between the wheel and the axle, and there are a few easy ways to do that: sanding and polishing the axles as well as using graphite or teflon as a lubricant. (Our troupe doesn’t allow graphite because it marks the floors, but teflon is allowed.)
3) Reduce the friction between the car and track. The best way to do this is to make sure your wheel alignment is as straight as possible as this will keep it from rubbing against the center of the track.
The winner of our pinewood derby actually had a very blocky car designed to look like a platypus. I’m guessing the winner didn’t spend much time focusing on aerodynamics and instead chose to minimize their frictional losses.
Outnumbered January 5, 2012
Posted by mareserinitatis in gifted, math, teaching, younger son.Tags: math, teaching, younger son
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Today I’m going to be working with the elementary students again. This will be interesting as I completely switched gears from what we were doing before. The stuff we were doing before was fun, but as we move through the book, it looks like they need a lot of multiplication and division…which most second graders don’t have.
Today, we’re going to learn about other number systems. In particular, I’m going to have them pick a number using Indo-Arabic numerals and ‘translate’ into other numbering systems – Egyptian, Roman, Babylonian, Mayan, and Chinese. This will give us an opportunity to talk about different bases, positional numbers (i.e. the concept of place value), and how many systems don’t have a zero. (Although, there’s debate in some cases.)
After doing the prep, I’m SO glad that we don’t use the Babylonian system. Base 60?! No wonder my math professor got annoyed when we used degrees.
Thanks to the MacTutor History of Mathematics Archive for the picture!
Wordless Wednesday December 28, 2011
Posted by mareserinitatis in family, Fargo, food/cooking, pets, photography, younger son.add a comment
Wordless Wednesday December 21, 2011
Posted by mareserinitatis in family, food/cooking, math, older son, personal, pets, photography, religion, younger son.Tags: cooking, food, Gigadog, hannukah, older son, younger son
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Your son plays with…girls. February 20, 2012
Posted by mareserinitatis in education, feminism, gifted, older son, societal commentary, younger son.Tags: feminism, gender equity, sexism, social skills, socialization, stereotypes
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We had parent teacher conferences recently. While they overall went fairly well, there was one part of the discussion that bothered me. The teacher seemed concerned that the younger son spent more time playing with girls than boys.
I think that what gets me about this is that I’ve heard it almost every year that either one of my kids has been in school. Every time I hear it, I have the same reaction: “So?”
I can’t remember where I came across this bit of info, because I first found it when the older boy was in elementary school. It turns out that kids that are gifted are more likely to be androgynous and make an effort to actively choose their interests rather than following prescribed “gender-appropriate” behaviors.
This was a huge relief for me for many reasons. First, my sons have had interests in things like barrettes and finger nail polish, Dora, My Little Pony, etc. I assumed it was normal curiosity that most kids had, but maybe not. However, I’ve made an effort not to impose gender stereotypes on them unnecessarily. I’ve also noticed that there’s a lot more rough and tumble and even some bullying that goes on with boys. My boys aren’t into that, so it seems obvious that they would be more interested in playing with girls.
Second, it was a personal relief. I work in a couple of fields that are mostly male, and when I feel comfortable with it, I can be rather confrontational and direct. I was more interested in Legos than Barbies, and in school, I liked math and physics. It’s nice to know that I’m not “weird” for a woman…even though I am apparently different.
If I ever needed proof that there are some aspects of gender that are socially prescribed, I’ve gotten it over and over in this one question. I’m sure my parents got the opposite – your daughters are tomboys. What surprises me about this is that people really get so worked up about it. Why aren’t they surprised when girls and boys don’t want to play together?